Ive been hearing this complaint a lot and yes i agree its tough to grasp, but please, so was the rest of the movie. Futhermore, the movie was long enough, did you really want to see them loading kong into the boat, tying him down, further sedating him, and sailing back to new york?
And yeah it was hard to take Jack Black seriously, I agree. But it wasnt any fault in his acting, it was because you and I expected to see him in a comedic role, which we're used to. He still did a good job